The present invention relates to a centrifugal fan device used for cooling a heating element, such as a microprocessor unit (hereinafter called an “MPU”) mounted in a housing of an electronic device, as well as to an electronic device having the fan.
Movement toward speedup of data processing in a recent computer is considerably rapid, and the clock frequency of an MPU is markedly higher than ever.
Consequently, the amount of heat emitted by the MPU is increased, and there are required a method for directly cooling a heat sink by means of a fan and a method for forcefully cooling a radiator; namely, a heat sink module formed by thermally connecting a heat-receiving element to a heat-radiating element by use of a heat pipe, as well as a method for bringing a heat sink having a radiator fin into contact with a heating element, to thus dissipate heat, as in the related art. It is also indispensable to forcefully circulate a liquid coolant exhibiting high thermal conductivity by means of a pump and forcefully blow air on the heating element by means of a centrifugal fan device. Further enhancement of cooling performance of the fan and an additional reduction in size and thickness of the fan are required.
Enhancement of cooling performance of the centrifugal fan device is greatly dependent on an improvement in air-blasting performance of the fan, such as increased air quantity, increased static pressure, or other factors. In addition, even when air is blown uniformly over a wide range at an air outlet of the fan, heat is efficiently exchanged with; e.g., a radiator fin disposed at the air outlet, and hence the cooling performance of the fan can be enhanced greatly.
FIG. 10A is a side view showing the inside of a casing of a centrifugal fan device of the related art, and FIG. 10B is a partial cutaway view of the casing of the fan device of the related art.
A centrifugal fan device 101 is equipped with a sirrocco fan 103 disposed in a helical casing 102, and a motor 14 for rotating the sirrocco fan 103 is provided on one face of the casing 102. An air inlet 105 is formed in a face of the casing opposite the face provided with the motor.
The helical casing 102 is formed from sidewalls 121 and 122, which are parallel to each other, and an outer peripheral wall 123. An airway 106 for wind resulting from rotation of the sirrocco fan 103 is created in the casing 102, and the outlet 107 is opened in the end of the airway 106.
In the centrifugal fan device 101, an outer peripheral wall 123a of the casing 102 continuous from the casing nose section 109 parallel to a rotary shaft 108 of the sirrocco fan 103 is formed so as to spread toward the outlet 107. There is provided an outlet portion 107a which opens widely at the end of the casing 102 by means of widening end sections 121a and 122a of both sidewalls in association of the spread of the outer peripheral wall. The position and angle (A) of the nose are changed downwardly when compared with the position and angle of a related-art nose, to thus move the casing nose section 109 and make an opening area wider. The wide outlet 107 having a straight section 110 is opened at the leading end of the casing nose section.
A partition board 111 is provided between the sidewalls 121 and 122 of the casing 102 from the airway 106 to the wide outlet 107.
The centrifugal fan device 101 rotates the sirrocco fan 103 by means of rotation of the motor 104, thereby transforming the air taken in through the air inlet 105 into a swirling wind and causing the thus-swirled wind to pass through the airway 106 and to exit from the wide outlet 107 opened at the end of the casing 102.
The partition plate 111 of the centrifugal fan device 101 is disposed so as to divert the wind delivered from the airway 106 into essentially-equal parts. The wind is diverted, in an essentially-equal manner, between an airway 112 on the nose side and an airway 113 on a side counter to the nose side. The thus-diverted winds are guided so as to spread as they approach the wide outlet 107 and can flow out of the entire exit of the wide outlet 107 in an essentially-uniform manner.
The centrifugal fan device 101 guides the wind by means of splitting the airway of the widely-enlarged outlet section into the nose-side airway and the counter-noise-side airway in an essentially-uniform manner, and the wind uniformly flows out of the entirety of the wide outlet 107. Hence, a decrease in air-blasting performance, which would otherwise arise in such a related-art centrifugal fan device not having the partition plate 111, can be prevented.
Consequently, the centrifugal fan device 101 is effective for blowing an air over or cooling a wide range, such as for the purpose of cooling batteries of an electric vehicle equipped with a large number of batteries; for instance, a hybrid car.
The partition plate 111 is provided at a position different from the previously-described position or provided at a different angle of inclination, whereby the direction of or the amount of an air flowing out of the wide outlet 107 can also be changed (Patent Document 1).
In another related art, though unillustrated, an air blower using a cross flow fan is available. There has also been proposed an air blower in which one airway partition plate or a plurality of airway partition plates are provided in an airway close to an air outlet for splitting the airway into airways; the flow of an air becomes stable within the airways by virtue of the partition plates; and occurrence of an air stripping phenomenon is prevented, thereby diminishing noise attributable to stripping sound (Patent Document 2).    [Patent Document 1] JP-A-2003-336600 (FIGS. 1 and 2 on page. 5)    [Patent Document 2] JP-A-2004-278473 (FIGS. 1 and 3 on page 8)
However, in the related-art centrifugal fan device 101 such as that mentioned above, the partition plate 111 assumes a mere plate-like shape, and the partition plate 111 is formed over the entire height of the airway 106. Hence, the centrifugal fan device suffers a problem of, among the airs diverted into the airways 112 and 113 in an essentially-equal manner, particularly the air diverted into the airway 113 encountering difficulty in smoothly flowing up to the wide outlet 107.
Specifically, the flowing direction of the air is forcefully changed so as to spread toward the nose-side airway 112 while the air blown by the sirrocco fan 103 is incessantly colliding against a portion of the face of the partition 111 facing the sirrocco fan 103.
However, the air is difficult to flow in the vicinity of a face located at a position opposite the face facing the sirrocco fan 103 of the partition plate 111, and the speed of the air located in the vicinity of the opposite face is decelerated greatly. Thus, a pressure difference has become ease to arise between the air located in the vicinity of the opposite face and the air flowing in the vicinity of the outer peripheral wall 123 of the airway 113.
Consequently, the partition plate 111 entirely acts as great resistance to the airway and also as a factor for generating an eddy current or air turbulence on the side opposite the face of the partition plate facing the sirrocco fan 103. Hence, when compared with the air flowing out of the related-art centrifugal fan device, an air can be discharged uniformly from the wide outlet 107. However, there still exists a problem of difficulty being encountered in increasing the overall amount of air blast over a wide range at the air outlet as a result of the air partially failing to smoothly flow as mentioned previously.
The air blower using the related-art cross flow fan, such as that mentioned previously, is enhanced in terms of stability of an air blow, thereby achieving reduced noise. However, the air blower encounters difficulty in uniformly blowing an air over a wide range at the air outlet.